The present invention relates to an all-plastic, tamper-evident overcap for the closure portion or component of a shipping and storage container. This container which is typically a steel drum includes a drum end or head which typically includes a closure for dispensing the contents of the container and a closure for venting the container. More particularly the present invention relates to a tamper-evident overcap which is constructed and arranged to snap fit onto a portion, typically a radially extending lip or circumferential edge, of the corresponding steel drum closure.
In one embodiment of the present invention a frustoconical outer skirt is connected to the cap by a series of frangible elements. In a related embodiment the outer skirt, while still tapered to some degree, has a more cylindrical appearance and comprises the outer wall of the overcap, prior to separation from the snap-on cap. In both embodiments the overcap is unable to be removed without cutting or tearing away the snapped-on cap portion or without removal of the skirt so that the cap portion can be pried off. Either approach provides a visible indication of a tampering attempt. If the skirt is removed by breaking the series of frangible elements that connect the skirt to the cap, it is then possible to pry off the cap from its snap-fit onto the closure, without giving any further indication of a tampering attempt. However, the absence of the skirt, if unauthorized, would visually indicate a tampering attempt.
The present invention is directed to use with large shipping containers or drums where one drum end is arranged with a plug-type closure and an internally-threaded fitting, typically with a threaded interfit between the two. Due to the limited thickness of the drum end material and the desire to create an internally-threaded dispensing port, an internally-threaded fitting or flange is typically anchored into the drum end or head so as to provide a dispensing opening. The method of anchoring the flange fitting into the drum end involves the forming or drawing of the drum end material into a raised and shaped pocket. The next step is to place the flange fitting into the pocket and then form or crimp the metal of the drum end onto and around the flange fitting so as to anchor these two components together. The flange fitting is internally threaded and receives a closing plug and cooperating annular gasket in order to seal closed the internally threaded aperture defined by the flange fitting. Threaded removal of the closing plug enables the contents of the drum to be dispensed.
Without some type of tamper-evident feature, the closing plug could be removed at virtually any time, such as during shipping or storage, without being noticed. This would mean that someone could tamper with the drum contents without being discovered. This tampering could include partial removal of the drum contents and/or contamination of the drum contents by a foreign substance. Having a tamper-evident feature provides a desirable enhancement to the plug-flange fitting combination. It then becomes important to configure a tamper-evident feature which is reliable, easy to install or assemble, and relative inexpensive. The unitary, molded plastic design of the present invention satisfies the xe2x80x9cinexpensivexe2x80x9d criteria. The snap-on or snap-fit design of the present invention satisfies the xe2x80x9ceasy to installxe2x80x9d criteria and cooperates in satisfying the xe2x80x9creliablexe2x80x9d criteria. The use of a removable (i.e., frangible) skirt as disclosed by the present invention satisfies the xe2x80x9creliablexe2x80x9d criteria and does so in a novel and unobvious manner.
One of the keys to the success of the present invention is the placement of the underside (i.e., lower) edge of the frangible skirt against the surface of the drum end or at least in extremely close proximity to the surface of the drum end. By not leaving any noticeable clearance space or at most a space with only a few thousandths of an inch gap, there is effectively no room for a blade or edge of any type of utensil, implement, or hand tool to slide beneath the frangible skirt in hopes of removing the cap without this attempt being revealed by the fracture of one or more of the connecting frangible elements. As will be clearly explained, any such inserting and prying attempt causes the fracture of at least one of the frangible elements and this is sufficient to reveal (visually) that a tampering attempt has been tried. This tamper-evidencing feature is further enhanced by the dimensioning of the skirt relative to the snap-on portion such that with the nominal dimensions present the skirt is actually preloaded against the upper surface of the drum in one embodiment of the present invention. In a related embodiment of the present invention, the axial and radial spacing between the lower edge of the skirt and the lower edge of the snap-on lip of the cap are such that direct contact between the lower edge of the skirt and the upper surface of the drum end is not needed.
A unitary, plastic, snap-on overcap for providing a tamper-evident capability to a closure assembly of a container according to one embodiment of the present invention comprises a cap, a removable skirt, and a plurality of spaced-apart frangible elements connecting together the removable skirt and the cap. The closure assembly which is anchored to the container includes an internally-threaded fitting and a closing plug which is threadedly installed into the fitting. The cap portion of the overcap includes a depending sidewall which terminates in a snap-on lip portion. The removable skirt includes a wall portion which is constructed and arranged to be positioned in close proximity to an upper surface of the container when the cap is snapped onto the closure assembly. The snap-on assembly involves the lip portion of the cap engaging a cooperating lip portion of the closure assembly. Access to the lip portion of the cap in order to pry the cap free from the closure assembly is not possible until the skirt is removed from the cap, a step which requires the severing of the plurality of spaced-apart frangible elements.
One object of the present invention is to provide an improved unitary, plastic, snap-on overcap for providing a tamper-evident capability.
Related objects and advantages of the present invention will be apparent from the following description.